Distillation of lubricating stock



March 29, 1932.

M. H. TUTTI.: DISTILLATION OF LUBRICATING STQGK Filed Aug. '7, 1929 3 Sheets-Sheet INVENTQR.

ATTORNEYS.

Filed Aug. 7, 1929 5 Sheets-Sheet 2 3 sheets-sheet s Mardi 29; 1932- M. H. TUTTLE DSTILLATION OF LUBRICATING' STOCK.

Filed Aug. T. 1929 Patented Mar. 29, 1932 1,851,550

UNITED STATES PATENT OFFICE'v MALCOLM H. TUTTLE, F vNEW ROCHELLE, NEW YORK DISTILLATION OF LUBBICATING `STOCK Application led August 7, 1929. Serial No. 384,031.

This invention relates to the distillation of pressure distillation because ofthe pressure -lubricating stock from paraffin or mixed base required to cause vapor to flow upwardly crude oil. through the bubble decks, thus resultin in a An object of this invention is an improved higher pressure at the point of fee and '5 -method of and apparatus for obtaining a points of removal of liquid fractions than is 55 large yield of overhead cylinder stock under maintained at the point of removal of the conditions such that negligible decomposition vapors, thereby causing less vaporization occurs and the composition of the stock is than if the pressure throughout the tower controllable. Were the same as at the point of vapor disln According to this invention, charging stock charge. However, the subjection of the 60' which. may be paraffin or mixed base crude liquid fractions to vacuum reboiling and the oil from which the low boiling compounds use of the distillate thus obtained as reflux in have been removed, is subjected to fractional the bubble towerresults in the obtaining of distillation at low absolute pressure to sepamaximum vaporization of the volatile conrate the major. portion of the lubricating stituents of such fractions and alsofin the 65 stock and the: unvaporized charging stock is obtaining of `sharp fractionation. The pressubjected to reboiling at lower absolute pressure in the reboiler is the same, or lower than sure to effect further vaporization of lubrithat maintained in the top of the bubble cating stock which is condensed and utilized tower and this combination permits the nal 2o as reflux in the fractional distillation operastripping from the charging .stock of its 70 tion. The fractional distillation preferably lighter fractions at the lowest possible pres-" is effected by means of successive heating opsure. Italso permits return to the bubble erations and the utilization of a lportion of tower of liquid having a boiling point range the charging stock as recycle stock. Steam low enough for fractionation in the bubble preferably is used to assist vaporization of tower at the higher pressure. 75' the lubricating stock and preferably conden- Other objects, novel features and advansate occurring in an intermediate zone of the tages of this invention will be apparent from fractional distillation operation is subjected the following specification and accompanyto re-distillation under reduced absolute presing drawings, wherein:

sure to separate the same into products of Fig. 1 discloses an apparatus for effecting 80 boiling points intermediate to those of the distillation in accordance with the invention. distillate from the fractionating operation Fig. 2 discloses' a modified form of an apand the unvaporized residuum. paratus, and

In lubricating stock obtained according to Fig. 3 discloses a further modification.

this invention, the wax remains in amorphous Referring now to Fig. 1, charging stock 85 form when chilled to 409 F. The fracwhich may be paraflin or mixed base crude oil tions containing wax are separated from the from which the low boiling compounds have charging stock in the first'vaporizing operapreviously been removed, is forced from the tion at a temperature which is insufficient to tank 1 by the pump 2 through the pipes 3 and l crystalize the wax and only the fractions 4 to the heating element 5 of a tube still. G 9.@ which contain substantially no wax are subin which the stock is discharged through the jected to higher temperatures. pipe 7 into the bubble tower 8, at a temper-af The distillation operation is carried on ture ranging from 600 to 700 F.y Vaporizaf preferably at sub-atmospheric pressure and tion occurs within the tower 8 andthe vapo *'5 the temperatures to which the charging stock pass upwardly through the bubhl is subjected are such that negligible deconi- While the non-vaporized portions pass down?" position occurs. Fractionation is preferably Ae-'ardly through additional bubblefdecksl to effected by use of a bubble tower by which the base of the tower. The ascending vapors sharp fractionation is obtained, although a encounter refiux liquid supplied tothe tower' bubble tower is not in itself suited to low as will subsequentl be described andthe mi;

i fractionated vapor is conducted from the top of the tower through the pipe 9, the temperature of the vapor ranging from 300 to 400 F. The pipe9 leads to a surface condenser 10, which is connected by pipe 11 with a vacuum pum 12. The vacuum pum 12 maintains the dbsired pressure in the bu ble tower 8 and also removes the uncondensible gases formed in the distillation operation.

The non-vaporized portion of chargin stock encounters ascending vapors supplie to the base of the bubble tower as will be subsequently described, these vapors being of higher temperature than the iquid stock. The liquid collecting in the base of the bubble tower is drawn by the pum 13 through the pipe 14 and is forced throug the pipe 15 into the secondary heating element 16 of the tube still 6. From the tube still, the heated liquid is conducted b the pipe 17 and is discharged into the reboi ing or vaporizing chamber 18 at a temperature between 675 and 775 F. The vaporizer 18 communicates with the bottom of the bubble tower 8 and the vapors produced in the vaporizer pass into the buble tower and flow upwardly therethrou h. These vapors volatilize lower boiling point constituents from the downwardly flowing liquid stream and the vapors thus formed pass into the upper section of the bubble tower where they are subjected to fractionation along with the vapors resulting from the first vaporizing o ration. The condensate produced in the a ove operation collects in the bottom of the bubble tower 8 and is recycled through the secondary heating element 16. Steam may be introduced into the vaporizer 18 throu h the pi e 19 controlled by the valve 20 to ecrease t e partial pressure.

of the oil and thereby increase the amount of vapo'rization.

The unvaporized stock collects in the base of the vaporizer 18 and is conducted by pipe 21 controlled by valve 22 to a vacuum reboiler 23. The upper portion of the reboiler 23 is connected b a pipe 24 with a surface condenser 25, which in turn is connected by pipe 26 with the vacuum pump 60. A pi e 27 is provided to reflux condensate from the condenser to the bubble tower 8 and has two points of connection with the tower, valves 28 and 29 being provided to control the flow into the tower. The unvaporizedv charging stock is supplied to the vacuum reboiler l23 at temperatures between 650 and 750 F. and the vapors are discharged through the pipe 24 at temperatures between 600 and 700 F. The temperature of the reflux condensate fromv the condenser 25 ranges from 400 to 500. F. Steam may be introduced into the reboiler 23 through the pipe 30 controlled by the valve 31 and the unvaporized stock in the reboiler is withdrawn through pipe 32 by' the pump 33 and caused 35 and` valve 28, the heavier fractions of ascending vapor are condensed and removed throu h the pi e 41 to the reboiler 37 which is maintaine at lower absolute pressure than exists in the bubble tower 8 at the inlet to the pipe 41. Steam may be admitted to the base of the vacuum reboiler 37 through a pipe 42 controlled by valve 43, therebydecreasing the partial pressure of the oil. The reduction of the partial pressure, together with the low absolute pressure maintained in the reboiler produces vaporization of the lighter fractions. Such vapors are conducted through the pipe 38 to the surfacecondenser 39 in which the non-condensible gases are removed and the liquid in the condenser is conducted by pipe 44 to the run-down tank 45. The unvaporized fractions are conducted from the vacuum reboiler through the pipe 46, cooler 47 and pipe 48 to the run-down tank 49. The temperature of the side-cut withdrawn from the bubble tower ranges from 400 to 500 F. and the vapor produced in the vacuum reboiler 37 ranges from 350 to 450 F. while the unvaporized fractions range from 350 to 450F. The vacuum pump 12 removes the non-condensible gases from the bubble tower and also maintains the bubbletower under low absolute pressure. The pressure in the vacuum reboilers is maintained'by the vacuum pump 60 as low at least as the pressure maintained at the top of the bubble tower, but at lower pressures than are maintained in the sections of the bubble tower with which they are connected.

The vapors conducted from-the top of the bubble tower through the pipe 9 are conldensed in the surfaceccondenser 10 and the condensate is discharged through the pipe 50 into the run-down tank 51. The amount of liquid condensed in the bubble tower 8 and the degree of fractionation is controlled by returning reflux from the tank 51 to the top of the bubble tower. The reflux is drawn through the pipe 52 by the ump 53. and passed through the pipe 54 and temperature control valve 55 to the bubble tower.

' Heavier liquid fractions may also be returned to the bubble tower by drawing liquid from the run-down tank 45 by the pump 56 through the pipe 57 and conveying such liquid through the pipe 58 and temperature control valve 59 at a point below the point ing possible to control theI amount of the higher boiling point hydrocarbons in the side fractions.

Withthis form of apparatus, light disv'of removal of the side fraction, thereby mak- A tillate, heavy distillate and overhead cylinder stock are obtained. The conditions under which these products are obtained are such that ne ligible decomposition occurs and the composition of these products is controllable through the medium of the various reflux liquids. The successive heating operations make it possible to obtain fractions containing wax in which the wax remains in amorphous form when chilled to 40 F.. rfhe vapors produced by the second vaporization operation, b reason of their contact with the unvaporizec remainder from the first vaporizing operation insure complete removal from the charging stock of the lower boihng constituents so that none of them are subjected to the second heating.

Referring to Fig. 2, charging stock 1s drawn from the tank la by the pump 2a through the pipe 3a and is conducted vby the pipe 4a to the heating element 5a of the tube still 6a from which it is discharged bythe pipe 7a into the bubble tower 8a.'. Vapor 1s conducted from the top of the bubble tower 8a by the pipe 9a to the surface condenser 10a which is connected by the pipe 11a with the vacuum pump 12a. Unvaporized charging stock collecting in the base .of the bubble tower 8a is withdrawn by the pump 13a from the pipe 14a and supplied by the pipe 15a to the secondary heating element 16erl of the tube still 6a and is discharged from the heating element through the pipe 17a into the vaporizer 18a which communicates with the base of the bubble tower 8a. A pipe 19a controlled by a valve 20a is provided for supplying steam to the evaporating chamber 18a. A pipe 21a leads from the base of the vaporizing chamber to a reboiler 23a, the top of which is connected by a pipe 24a with a surface condenser 25a which is connected by pipe 26a wit-h the vacuum pump 60a. A pipe 27 a leads from the surface condenser 25a to the top of the bubble tower 8a to provide reflux condensate. A pipe 50a leads from the surface condenser 10a to the run-down tank 51a in which the distillate is collected. A pipe 30a controlled by valve 31a'l is provided for supplying steam to the reboiler 23a to assist vaporization. The unvaporized o il in the reboiler 23a is withdrawn by the pipe 32a and is delivered by the pump 33a through the pipe 34o to the cooler I35a from which it is conducted by the pipe 36a to the tank 37a. The operation of the system disclosed in Fig. 2 is generally similar to the operation of the system disclosed in Fig. l except that no side cut is taken and no reflux is used except that obtained from the surface condenser 25a. The unvaporized charging stock from' the first vaporization operation is additionally heated to provide higher boiling point vapors which are discharged from the vaporizer 18a into the base of the bubble tower 8a. Likewise, the unvaporized stock from the second vaporization operation issubject to decreased pressure in the vacuum reboiler 23a to effect further va orization and to 'supply reflux for use in t e bubble tower 8a.

In the modification disclosed in Fi 3,

charging stock is drawn from the tan v16 by the pump 26 through the pipe 36 andv isl conducted bythe pipe 46 to the heating element 56 of the tube still 66 from which it is discharged by the pipe 76 into the bubble tower 86 at a point approximately half way 'between the top and bottom of the tower.

Vapor is conducted from the top of the bubble tower 86 by the pipe 96 to the surface condenser 106 which is connected by the 116 Vwith the vacuum pump 126. Unvaporized chargingstock collecting in the base of the bubble tower 86 is conducted through the.:

pipe 216 controlled by the valve 226 tothe vacuum reboiler 236, A pipe 246 conducts vapor from the reboiler 236 to a surface condenser 256 which is connected by the pipe 266 with the vacuum pump 606. A pipe 276 leads from the condenser 256 to the to'p of the bubble tower 86 to provide reflux condensate therefor. The pipe 506 leads from the condenser 106 to the run-downtank 516 in which the distillate is collected. A pipe 306 controlled by the valve 316 is provided for supplying steam to the reboiler 236 to assist vaporization. The unvaporized oil in the reboiler 236 is withdrawn by the pipe 326 and is delivered by the pump 336 through the pipe 346 to the cooler 356 from which it is conducted bythe pipe 366 to the tank 376.

ln this apparatus, the residual oil'from the vaporization operation is reboiled at lower absolute pressure to'effect further vaporization and` supply reflux for use in the bubble tower 86. The pressure in the top of the bubble tower may be the same as that :in the vacuum reboiler,but the pressure on the liquid stock in the lvacuum reboiler is less than -the pressure to which liquid in the base of the bubble tower is subjected.

A three-way valve is providedin each of the pipes 11, 11a, and 116 by means of which the bubbletowers may be connected to the vacuum pumps, 12, 12a and 126, respectively or may be put in communication with the atmosphere. This makes it possible to carry out the distillation either under sub-atmospheric or atmospheric pressure as is desired.

- um pump 12 need handle only the non-condensable gases. With some lubricating stocks, it is possible to operate the bubble tower above 40 millimeters absolute and in some cases the bubble tower may be o erated as high as atmospheric pressure. n such cases, the reboilers may be operated at absolute pressures of from 10 to 40 millimeters.

It is, of course, understood that other forms of apparatus may be used to carry out the process described and that various structural chan es may be made in the apparatus disclosed without in any 'way departing from the spirit of the invention as defined in the appended claims.

I'claim:

1. The method which comprises subjecting lubricating oil stock to fractional distillation at low absolute pressure, reboiling the unvaporized stock at lower absolute pressure, condensing the vapor from said reboiling operation, and utilizing the condensate thus obtained as reflux for the fractional distillation operation.

2.v The method which comprises subjecting lubricating oil stock to fractional distillation at low absolute pressure, additionally heating the unvaporized portion of the lubricating oil stock and supplying the vapor thus obtained to the fractional distillation operation, reboiling the liquid remainder at lower absolute pressure, condensing the vapor from said reboiling operation, and utilizing the condensate thus obtained as reilux'for the fractional distillation operation.

3. The method which comprises subjecting lubricating oil stock to fractional distillation at low pressure by successive heating operations and with recirculation of a portion of the stock during the second heating operation. reboiling the unvaporized stock at lower absolute pressure, condensing vapor from said reboiling operation and utilizing the condensate thus obtained as reflux for the fractional distillation operation.

4. The method which comprises effecting fractional distillation at low absolute pre`ssure of lubricating oil stock by two successive heating operations and reclrculation of a portion of the stock during the second heating operation, reboiling the unvaporized stock at lower absolute pressure, condensing vapor from said reboiling operation, utilizing the condensate thus obtained as reux for the fractional distillation operation, subjecting afraction produced in the fractionall distillation operation to reboiling, and separately collecting the condensate land the unvaporized portion.

5. In a distillation system, a fractionator, means for supplying heated lubricatin oil stock to said fractionator at an intermediate point,'means foramaintaining low absolute pressure in said fractionator, a reboiler, means to conduct liquid from said fractionator to said reboiler, means for maintaining the pressure in said reboiler at least as low `as the lowest pressure in the fractionator,

means for condensing vapor from said reboiler, and means for reiuxing to said fractionator condensate thus obtained.

6. In a distillation system, a fractionator, a heater, means for supplying lubricating oil stock through said heater to said fractionator at on intermediate' point, means fory maintaining low absolute pressure in said fractionator, a reboiler,'mea-ns to conduct liquid from said fractionator to said reboiler, means for maintaining the pressure in said reboiler at least as low as the lowest pressure in the fractionator, means for condensing vapor from said reboiler, means for reluxing to said fractionator condensate thus obtained, a lvaporizer communicating with the lower portion of said fractionator, a second heater,

and means for-conducting liquid from said fractionator through said second heater to said vaporizer.

' 7. The method which comprises heatin lubricating oil stock to effect vaporization 0% low boiling fractions, fractionating the Vapor thus obtained under low absolute pressure, reboiling the unvaporized fractions and condensate from the fractionating operation at higher temperature, subjecting the vapor thus obtained to fractionation with the lower boiling vapors, reboiling the residual liquid at lower absolute pressure, condensing the vapor thus obtained, and utilizing the same as obtained, and utilizing the same as reiux in the fractionating operation.

9: In combination, a heater, a fractionating column, a conduit leading from said heater to said fractionating column, a reboiler, a conduit leading from the fractionating column to the reboiler, means for maintaining an absolute pressure in the reboiler lower than the lowest pressure exist-ing in the fractionating. column, and means for conlib' densing the vapors produced by the reboiler and returning the same to the fractionating column as reflux.

10. In combination, a heater, a fractionating column, means including said heater to deliver lubricating oil stock to the fractionating column at a temperature sutlicient to cause vaporization, a plurality of reboilers, means Jfor heating the residual oil from the frictionating column and charging it to the first reboiler, means for maintaining low absolute pressure on the ractionating column and said irst reboiler, means for returning to the base of the fractionating column vapors produced in the first reboiler, means for Vdischarging residual oil from the first reboiler to the second reboiler, means for maintaining lower absolute pressure in said second reboiler than in said first reboiler, means for removing` and condensing vapors producd in the second reboiler, and means for returning such condensate to the fractionating column as reux.

11. In combination, a heater, a fractionating column, a conduit leading from said heater to said fractionating column, a reboiler, means for conducting liquid fractions from the fractionating column to the reboiler, means for maintaining the pressure in said 3o reboiler lower than the lowest pressure in the fractionating column, means for condensing the vapors produced inthe reboiler, and means for returning the same to the fractionating column as reiluX.

12. In a system for the distillation of lubricating oil stock a, heater, a fractionating column, a conduit leading from said heater to said fractionating column, a reboiler, means for conducting liquid from the fractionating column to the reboiler, condensers connected to said fractionating column and reboiler, means for maintaining the same absolute pressure at the outlet of each condenser, and means for returning condensed 46 vapor as reflux tothe fractionating column from one or both of said condensers.

In testimony whereof I have signed my name to this s ecifcation. LCOLM H. TUTTLE. 

